The field of the present invention relates generally to semiconductor fabrication and more particularly, to a method of planarizing photoresist.
Historically, when lines, vias and other features needed to be created during the semiconductor fabrication process, they were created in and on durable substrates, e.g. silicon, silicon oxide, silicon nitride, aluminum and aluminum alloy. Since most depositions of materials are conformal, the features usually need to be planarized so that there is a xe2x80x9clevelxe2x80x9d surface on which to build the ext layer. The non-planarity of a surface may be extensive in areas with a larger number of features at close or irregular intervals. There are a number of methods that can be used to planarize the surface of a substrate after the current level of features has been formed. It is generally agreed upon that the less complex processing steps are preferred over more complex processing steps. It is also generally agreed upon that the fewer processing steps per feature formation the better.
One of the disadvantages of using certain materials during semiconductor processing is that the materials must be cleaned before and/or after planarization. Some of the more common planarization methods include reactive ion etching (RIE) and chemical/mechanical polishing (CMP). Each method has its advantages and disadvantages. One of the advantages of RIE is that it is capable of removing substantially all of the materials currently used in semiconductor processing, including silicon, silicon oxide, silicon nitride, aluminum, aluminum alloy, polysilicon, photoresist, antireflective coating, silicides and silicon oxynitride. The cleaning of these materials can involve the use of chemicals that must be reclaimed and/or disposed of according to government guidelines. Other disadvantages of using certain materials when is that when deposits to be removed are greater than a certain thickness, certain planarization processes like CMP are less effective. In the past the use of CMP has meant that certain materials were thought to less suitable because they could degrade during the CMP process. One of the disadvantages of CMP is that the not all surfaces are xe2x80x9crigidxe2x80x9d enough to be polished. There are situations where it would be advantageous to use the CMP process if there were a material available which would both polish preferentially and be easily removed from the underlying layer.
As shown in FIG. 1, the conformal deposition of a layer, 5, of a material leaves portions of the material, 5, on regions of the surface other than the target region 5a. To remove the material from the untargeted regions and to planarize the last deposited surface, 5, the surface must be treated. A treatment usually includes CMP and/or RIE. RIE is usually used where the layer deposited is of sufficient thickness that the CMP process is less than optimally effective. However, if RIE is to be used, then the targeted areas, 5a, must be protected during the RIE process. Usually, the targeted areas are covered. When depositing a xe2x80x9ccoveringxe2x80x9d layer, 10, as shown in FIG. 2, it can be seen that covering layer, 10, is usually conformally deposited also. It can be imagined where the processing of each of the last two layers is complex it increases the complexities of the overall wafer processing. It would therefore be desirable to use a material for the covering layer, 10, that would not only xe2x80x9cprotectxe2x80x9d the targeted areas, but also help minimize the overall processing complexity. Photoresist is a material that tends to need less complex processing, but historically it has not been used in CMP processing. Thus, there remains a need for a method for CMP processing utilizing photoresists.
It is therefore an object of the present to invention to provide a method for CMP processing photoresists.
It is a further object of the present invention to provide a method for removing material deposited in untargeted areas.
In accordance with the above listed and other objects, we provide a method for polishing an object having a layer of photoresist, the method, comprising:
a) applying a layer of slurry on an a layer of photoresist on an object having a first and a second side, the layer of photoresist on one of the first and second side, the object having a center axis perpendicular to the first and second side;
b) contacting the layer of slurry with a pad having a first and second side, the first side of the pad exerting a force on the slurry.